Submit is indeed sending a request to the server. When you enter a value in a text field and then submit your page, the value will be stored in session state,which is a referece of all stored text fields during your current session (the period you are logged in to your application). You can use these stored values for reference in one page, or a cross pages in your application.

It is indeed possible to refresh only part of your page, say a region or a single field. It does however, cost a bit more work and understanding of apex. Given that you are new and familiarizing with apex, I'd wait with that for a bit.

Here you can find a picture of how your page layout should look with your page items and your button: